Formulating diets without alfalfa: Cleaning up the aftermath of the 2013 alfalfa winter kill
Lactating cow diets in 2013 may reflect the alfalfa shortage as producers will likely be feeding greater than 50% of diet dry matter as corn silage. For dairy producers, this is an unwelcome start to the late spring with elevated feed prices and the last two years of dry weather resulting in a shortage of feed, especially forage.
Why do we feed alfalfa? Alfalfa is palatable and is a good source of effective fiber to stimulate cud chewing and a healthy rumen. Alfalfa also provides soluble nitrogen for rumen bacterial growth and provides dietary calcium. Alfalfa also has a favorable amino acid profile providing lysine and methionine (key amino acids for both milk production and growth) in a beneficial ratio to match amino acids supplied by corn and corn co-products. Alfalfa also has a number of agronomic advantages and fits well with nutrient management plans.
To increase forage availability in 2013, many producers have seeded alternative forages into existing alfalfa stands or have plowed under existing alfalfa stands in favor of a fresh slate. Key attributes of successful forage options are those that establish quickly, grow rapidly, and provide good yield per acre. Experts have made many suggestions including ryegrass, sorghum-sudan grass, BMR sudan grass, clover, wheat, barley, oats, peas and oats silage, and to replace alfalfa acres with corn or soybeans. Nutrient composition for some alterative forage can be found in Table 1. As always, adequately sample forages and submit them to a commercial lab to determine the nutrient composition of the forages you are working with.
Producers have asked the question, "How do we feed cows without alfalfa?" We assembled several diets (Table 2) to demonstrate the effect of removing alfalfa from the diet and the effects on the nutrient composition.
Compared with our typical Midwestern TMR with 16 pounds of alfalfa DM per cow per day, the TMR in which we replaced all the alfalfa with corn silage has lower crude protein (CP) content, lower soluble protein, higher neutral detergent fiber (NDF), considerably higher starch, lower calcium, and reduced lysine:methionine ratio. The calculated cow performance from the "alfalfa-less" TMR is actually surprisingly similar to the typical Midwestern TMR.
Next we replaced alfalfa with feed byproducts such as cottonseed and soybean hulls. We were unable to affordably match the nutrient profile of the alfalfa diet with byproducts but predicted cows performance was still comparable to the typical Midwestern diet, albeit at a higher cost per cow per day.
In our final example diet, we replaced alfalfa with mixed grass silage and were able to assemble an acceptable diet but with a lower cost than the original Midwestern diet. When comparing these diets, it is critically important to consider the effects of forage on altering the rate of passage through the rumen and therefore the diet digestibility. Physical attributes of the diet, such as particle length, will have a considerable impact on cow productivity.
In addition to considering alternate forages and diet formulations, this is a great time to evaluate your options for storing forages to prevent shrink and increase efficiency of forage feeding. Finally this is a good time to evaluate potential cull cows including excessive numbers of replacement heifers. Consider options such as restricted feeding of growing heifers and exploring alternative non-forage fiber sources such as whole fuzzy cottonseed, soyhulls, corn gluten feed, beet pulp, and sweet corn silage.
The key take-home message here is that cows require nutrients not ingredients, so sourcing good quality palatable ingredients that meet the nutrient requirements of the cow based on level of production can result in as good, if not better, production compared to more traditional diets. The main nutrient deficiencies to watch for are low dietary calcium and soluble protein. Calcium in the diet plays a vital role in transition cow health and success. Consider making modifications to the protein mix to provide enough calcium and possibly adding slow releasing urea to increase the soluble protein in the diet. Consult with your nutritionist before making diet changes as shortchanging key nutrients or overfeeding other nutrients can have long-term effects on herd profitability.
Table 1. Nutrient composition dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and NDF digestibility (NDFd) of forages to replace alfalfa losses due to winter kill.
|Forage type, silage||DM, %||CP, %||NDF, %||NDFd, % 48 h||Energy, NEL Mcal/lb|
|Alfalfa, mid maturity||42.9||21.9||43.2||48.1||0.55|
|Wheat, early head||33.3||12.0||59.9||56.4||0.53|
|Sorghum sudan grass||28.8||10.8||63.3||57.2||0.49|
Table 2. Examples of total mixed rations (TMR) demonstrating the effects of diets without alfalfa.
|Typical Midwestern TMR||Alfalfa replaced with corn silage||Alfalfa replaced with byproducts||Alfalfa replaced with mixed grass silage|
|High moisture corn||11.5||8.0||11.0||11.5|
|Lactation protein mix||9.5||13.0||10.0||9.5|
|Mixed grass silage||0.0||0.0||0.0||16.0|
|Cost (4)/ton (as-fed)||119.50||124.96||145.71||115.86|
|Predicted nutrient composition|
|RDP, % of CP||65.9||63.8||60.0||64.7|
|RUP, % of CP||42.6||36.2||40.0||35.3|
|Soluble protein, % of CP||42.6||35.0||35.8||40.5|
|Lysine: Methionine ratio||3.56||3.48||3.39||3.33|
|Energy allowable milk production, lb/day||89.1||91.6||91.6||90.6|
|Protein allowable milk production, lb/day||92.2||91.8||90.4||89.3|
|Milk urea nitrogen, mg/dL||15.0||10.1||8.7||12.0|
|Milk: Feed ratio||1.59||1.65||1.62||1.59|